Competing Theories and Emerging Complexities Social relations are widely recognized to influence health and to impact health disparities. Despite theoretical advancements and methodological innovations, we still do not know: 1) how social relationships and support change with age or 2) when social relationships are most beneficial or harmful to health. The proposed research addresses these issues by extending the Social Relations, Age and Health Study (SRS) to examine three waves of data over 20 years and by investigating detailed changes in social relations over one year using both monthly assessments and multiple informants. Specifically, we propose to: 1) Analyze 3 wave longitudinal data over 20 years to test competing theories about age, social relations and health. A third wave of the SRS will allow for unique opportunities to specify the direction and shape of change in the structure and quality of social relations over time. 2) Conduct an in-depth study of support exchanges and social contagion with multiple informants in a one year monthly longitudinal web-based study. We will test the relative strength of the three hypothesized mechanisms of social contagion: induction, homophile and shared environment. 3) Examine whether 20 year longitudinal patterns of social relations predict short term changes in enacted support over one year and identify long-term patterns of support type that predict short-term health trajectories. These unique data will permit an unparalleled examination of competing exchange theories, e.g. altruism, developmental stake, support bank, and their association with health innovation. We propose theoretical (test of competing theories) and methodological (20 year longitudinal data, multiple perspective network data, and web based follow-up) innovations to clarify recent complex and contradictory findings concerning health and social relations. Impact Findings will impact scholarship on the link between social relations and health as well as public policy focused programs designed to improve health and decrease health disparities.